## Topic outline

• • Remember that you are not the only one studying physics and occasionally getting confused!  The good news is that there are thousands of resources on the internet designed to help you understand everything we cover. • ### Chapter 1: The Science of Physics; Measurement and Math

Important Concepts:
• Scientific Method
• Metric Units and Prefixes
• Scientific Notation
• Graphing and Analyzing Data
• Accuracy (correctness) vs. Precision (exactness)
• Dimensional Analysis (checking units)

• • ### Ch 2.2, 2.3 Acceleration, Kinematics, and Free fall

Acceleration and Kinematics Equations
How do we use kinematics equations to calculate one value when given other values?
Acceleration is the rate of change of velocity. a = (vf-vi)/t
You can rearrange this definition to get vf = vi + at
Using the fact that area under the v vs. t curve equals displacement, you should be able to derive d = vit + .5at2
From the first two equations, substituting to eliminate t,  2ad = vf2- vi2

Free fall is the motion of objects which have no forces on it other than gravity acting on them.

These objects move vertically, changing velocity at the acceleration of gravity, or if they are also moving sideways, follow parabolic trajectories.

• ### Ch 3.1: Vectors and Components

Remember that a vector is just a measurement that has both size ("magnitude") and direction.  Mass does not have direction, so it is a scalar.  Force does have a direction (for example, 34 N, pushing east), so it is a vector.

Vectors which point diagonally (according to whatever grid you are using) are complicated to add or subtract.  Therefore, we break the vectors into components which follow the grid axes.  Just as a point on a graph has x and y components, a vector which points diagonally down and right has a rightwardcomponent and a downwardcomponent.

We use trigonometry functions sine, cosine, and tangent to calculate the size of the components.

• ### Ch 3.4: Relative Motion

All motion is relative.  You might be "at rest" relative to the room around you, but moving at 800 miles per hour relative to the center of the planet as we go all the way the earth each day.  When you are riding in a train and flip a coin, you see it go straight up and down, but someone standing on the ground sees the coin also flying sideways at 50 miles per hour.

Important concepts:
The velocity of A relative to B ("vA-B") is the speed and direction of A, as seen by B.
This is equal to the difference in their velocities; vA-B = vA - vB

If an plane is moving through air that is also moving, relative to the earth, then the plane's velocity relative to the ground equals its velocity relative to the air, plus the air's velocity relative to the ground.  In other words, a plane pointed north, flying in wind blowing to the west, actually travels northwest.

• • • ### Ch.5 - Work, Energy, and Power

Work, Energy, and Power

Big concepts: Work is a change in energy.   If you give something more energy, you have done positive work.

Energy is converted from one form to another as anything happens.  For example, as a ball falls through the air, gravitational potential energy is converted to kinetic energy (as it speeds up) and heat energy (due to friction with the air).

Energy is conserved, whether in the flight of a projectile, the current running through a light bulb, or the decay of an atom.

Using energy conservation laws (Total energy at start = Total energy at finish) can make it much easier to solve many problems in mechanics.

Power is not the amount of energy transferred, it is the rate at which energy is transferred.  An small engine with little horsepower can still do the work to get your car up a hill, but it will take longer, since it can only generate a small amount of energy per second.

• ### Ch 6 - Momentum

Momentum and Impulse

Momentum equals mass times velocity.  (This is linear momentum, as opposed to rotational momentum, which is a little more complicated.)  When two objects collide or interact, momentum is transferred from one to the other.  THE TOTAL MOMENTUM REMAINS CONSTANT BEFORE AND AFTER THE COLLISION.

Impulse equals force times the amount of time the force is applied.  The impulse is also equal to the amount of change in momentum.  (Push harder on an object, for a longer time, and you will change its velocity more.)

• This topic • ### Ch 7.2 - Gravity and Kepler's Laws

Universal Gravitation

Students should understand the origins and uses of Kepler's Laws and Newton's Law of Universal Gravitation.  These laws can be used to calculate the speed and orbital period of planets and other satellites.  Students should also be able to explain the concept of weightlessness, and the general concepts of Einstein's Theory of Gravity.

• ### Simple Harmonic Motion and Pendulums - 16

Simple Harmonic Motion

Simple harmonic motion (SHM) is the sinusoidal motion caused when the restoring force is proportional to displacement, but in the opposite direction.  In other words, when you move something one way, a force tries to push it back the other way.  Common examples include pendulums, and masses oscillating on springs.

Stationary graphs of Simple Harmonic Motion.

In the graph below, the blue curve represents the position x of an object moving back and forth in SHM.  Note that position vs. time is in the shape of a sine curve.

The red and green graphs represent the velocity and acceleration of the object.  Note that velocity is 90 degrees out of phase with position, and acceleration is 180 degrees out of phase.  In other words, when the displacement reaches zero, the speed is at a maximum, and vice versa.  Meanwhile, the displacement and acceleration reach maximum at the same times, but they are opposite signs (opposite directions.)  Think about a real pendulum or mass on a spring and make sense of this graph. • • • • ### Topic 20

Scattering, Interference, and Diffraction of Light  • ### Topic 21

Static Electricity, Forces, and Fields Remember that opposites attract?  In this chapter, you will calculate exactly how much they attract (and likes repel) and learn how to move charges around to create positive and negative objects.

• • • • • 